while banging my head furiously trying to work out why my callback sequence did not work 😡 , I must have randomly typed in a search query, and I found the following bit of information:

The callback function [i:2dez1j9z][b:2dez1j9z]must[/b:2dez1j9z][/i:2dez1j9z] be stored in a [b:2dez1j9z]code module[/b:2dez1j9z]; attempting to store it in a [i:2dez1j9z]class [/i:2dez1j9z]or a [i:2dez1j9z]form [/i:2dez1j9z]module generates a compile-time error, “Invalid use of AddressOf operator.” 😮

thanks to [url:2dez1j9z]http://www.oreilly.com/catalog/vbanut/chapter/booklet.html#sect5[/url:2dez1j9z] for this. 😀